The present invention relates to a cartridge for receiving a paste-like material, especially a dental material, comprising a cartridge body having an outlet opening for dispensing the material, whereby the axis of the outlet opening extends laterally at a slant in the forward direction. The invention also relates to a dental applicator with an applicator body having an outlet opening at its forward portion and designed for dispensing a paste-like material, especially a dental material. The axis of the outlet opening extends at a slant laterally away from the applicator body.
Such a cartridge is, for example, disclosed in U.S. Pat. No. 5,938,439. The outlet opening of this cartridge is provided at the forward area of the cartridge whereby the dispensing device in this embodiment is a dispensing socket which extends laterally at a slant. The dispensing socket is comparatively long and has a comparatively limited cross-sectional area so that a corresponding flow resistance results for the dental material passing through the dispensing socket. However, in practice, this solution has been applied successfully when it is necessary to dispense low-viscosity dental materials which are completely dispensable when a dispensing plunger is introduced into the dispensing socket.
Furthermore, it has been suggested to provide a relatively short socket. This solution, with respect to flow-technological considerations, can be compared to the embodiment according to FIG. 2 of U.S. Pat. No 5,938,439. With it, it is possible to provide an only slightly reduced cross-sectional area for the dispensed dental material. Despite the relatively small reduction, the flow resistance however is relatively great, especially in devices in which a lateral deflection of viscous dental material is realized. In order to be able to deflect such viscous dental materials effectively to the side, it was long thought that substantial shearing forces must be overcome and the flow direction must be preadjusted to a certain flow length in order to produce again a flow that is approximately laminary after lowering the plunger.
Even though it is possible to design the dispensing socket in an arc shape with relatively large radius in the outward direction to thus provide favorable flow conditions, this would mean considerable material losses since the piston could not enter the right-angle curve of the dispensing socket as is conventional in the art.
Furthermore, there is often not enough space for such a curved embodiment. Therefore, various solutions with various compromises have been suggested in which the lateral projection extends only at a very small angle relative to the longitudinal axis of the cartridge body. The known solutions thus do not realize the desired considerable degree of lateral deflection of viscous dental materials despite the narrow design and the resulting easier maneuverability of the cartridge, especially of the cartridge tip.
It is therefore an object of the present invention to provide a cartridge for rather viscous materials as well as a dental applicator with which a considerable lateral deflection of the materials to be dispensed can be provided, even though the materials are highly viscous, without having to substantially increase the pressure forces. At the same time, however, a simple and inexpensive design of the cartridge or the dental applicator should be ensured.
This object is.inventively solved in that the outlet opening is provided in the forward end of the cartridge body itself and that the width of the outlet opening is especially different from the axial length of the outlet opening. In a preferred embodiment, the width of the outlet opening is greater than the axial length.
The object of the invention is also solved in that a dental applicator comprising an applicator body for receiving and dispensing a paste is provided that has a front end with an outlet opening for dispensing the paste material. The outlet opening has a width that is different from the axial length of the outlet opening; the width is especially greater than the length.
It is especially beneficial to provide the inventive outlet opening at the cartridge body itself. This, on the one hand, ensures that no laterally projecting protrusion impairs manipulation of the device so that filling of hard to reach cavities is not impaired. Surprisingly however, even rather deep cavities can be reached without problems. The lateral deflection angle of the dental material strand dispensed from the cartridge can be considerable, despite the minimal flow resistance, and can reach, for example, almost 90xc2x0. Experiments based on the present invention have shown that especially because of the increasing width, at least in portions of the cross-sectional area of the dental material strand dispensed from the outlet opening, the strand will bend rearwardly in a curved shape. Design variations of the deflection wall can be especially beneficial in this context.
It is especially advantageous that inventively the location of actual application, i.e., application of the strand of the material at the application location, is removed from the cartridge. The strand thus also serves simultaneously practically as a simulated dispensing socket. The stiffness and stability of the strand, aside from the effect of the high viscosity of the material, is affected substantially by two considerations. The asymmetric design of the outlet opening results in a relatively wide strand having flanks that act like ribs in a reinforcing way. Furthermore, the curvature that is imparted to the strand by the dispensing action gives the strand a somewhat improved stability. The curvature can be further enhanced by providing an inner radius or an inner curvature at the deflection wall which is positioned opposite the dispensing outlet opening.
It is understood that, aside from the preferred embodiment with a width of the outlet opening that widens from the rear to the front when viewed over the cartridge length, further suitable modified outlet openings can be realized. For example, by realizing a substantially diamond-shaped outlet opening a correspondingly shaped strand with a relatively high bending stiffness can be produced.
It is understood that the deformation resistance will increase when the strand geometry deviates to a greater extent from the circular cross-sectional shape of the cartridge body. On the other hand, it is inventively especially favorable that a relatively minimal deformation of the strand allows the realization of the inventive effect according to which the flow resistance for the high-viscosity material can be minimized. It is especially inventively preferred that no flow resistance obstacles such as thresholds or steps impair the dispensing action of the dental material from the cartridge body. It is especially preferred in this context when the outlet opening is practically a direct extension of the preferably substantially cylindrical cartridge body as regards the cylinder wall which is adjacent to the outlet opening.
Because of the flow-technologically beneficial design for producing the inventive strand, a surface reduction in the ratio of, for example, 1:2.5 between the cross-sectional area of the inner portion of the cartridge body and the outlet opening is possible without generating flow resistances that are too large.
According to a further especially favorable aspect of the invention, the cartridge has no part that is fixedly connected to the cartridge and would laterally project past the circumference of the cartridge. On the contrary, the inventive strand simulates substantially a laterally projecting dispensing socket. This means, on the other hand, that the inventive cartridge, if necessary, can be closed off without problems with a corresponding cover cap (50).